1. Technical Field
The present invention relates to a method for manufacturing thin films, and particularly to a method of manufacturing an organic electro luminescent (EL) device.
2. Background Technology
In recent years, electronic devices incorporating organic molecules, primarily organic electro luminescent (EL) devices, have begun to receive special emphasis in academia and industry. Echoing this trend, also from the aspect of processes, there has been an accelerating shift of attention from vacuum-based processes to solution processing, since the latter requires less energy. If one considers elements having multi-layer films manufactured by solvent-based processes, it is clear that the adjacent thin film layers must be formed with different solvent groups. In other words, assuming that one layer is formed with organic solvent, it is necessary that adjacent thin films, above and below that layer, be formed with aqueous solvents, which do not mix with the organic solvent. The reason is, if it is attempted to create contiguous layers of the same family of solvents, the two layers will mix together, defeating the purpose of creating distinct, sequential, multiple layers. Namely, each thin film manufactured by solvent-based processes is exposed to both solvent families: the solvent with which it is formed or wherein it dissociates, and the atmosphere of the layer onto which it was formed or of the layer formed on top of it. This fact poses a problem for functional thin layers. Some functional thin layers are known to be functionally degraded by exposure to another family of solvents. One example of this is the oxidation deterioration and shortened lifetime of polymers after exposure to water. There has also sometimes been inadequate control of the atmosphere to prevent atmospheric fouling, however, and this subject has not been adequately investigated. Nevertheless, since fouling is concentrated at the interface, the key to functional expression, prevention of atmospheric fouling is considered to be very important.